Plastic sealing composition



Patented June 1, 1937 PLASTIC SEALING COMPOSITIONv Byron V. McBride, Irwin, Pa., assignor to West inghousetElectric & Manufacturing Company,

vania East Pittsburgh, Pa., a corporation of Pennsylt, No Drawing. Application January 16, 1936,

Serial No. 59,418

6 Claims.

This invention relates to plastic sealing compositions.

In the manufacture of refrigerators, thermal contacts are provided between the refrigerator coils and the side of the food compartment in order to provide for efficiently conducting the heat from the food compartment to the refrigerator coils. The thermal contacts employed are usually formed by soldering the refrigerator coils 10 to the side of the food compartment. These contacts often prove to be inefficient since they are affected by moisture and corrosion sets in and destroys the contact.

An object of this invention is to provide a thermal plastic sealing composition.

Another object of this invention is to provide a thermal plastic sealing composition that is flexible at low temperatures and is not affected by moisture.

In plastic sealing compositions for use in refrigerators or the like, it is desirable to provide for the transfer of heat from one member to the other joined by the composition.

A good heat transfer may be obtained by employing a material having capacity for conducting heat as base for a plastic sealing composition.

In practice, it is found that either aluminum or copper in a finely divided state, or amixture of the aluminum and copper powders, may be successfully employed as the base or body of the composition to provide the required conductivity in the composition. In practice, metallic powders of a fineness such as will pass through a 400 mesh sieve may be employed although for practical purposes a coarser grade of the powders is satisfactory.

In order to hold the finely divided metals in a mass, and to provide a heavy viscous composition that is flexible at low temperatures and yet will not flow, a heavy viscous binder containing a non-drying oil is employed in conjunction with the finely divided metallic powder. A combination of a natural resin, copal, and a non-drying oil such as castor oil, provides a binder having the desired characteristics. In practice, the natural resins, damar, or kauri, may be employed in place of the copal.

The plastic sealing composition may be prepared by melting the copal at a temperature of between 175 C. and 235 C. until the frothing of the resin ceases, after which the castor oil is slowly added to the melted resin, the mixture being constantly stirred. The metallic powder is stirred into the mixture in order to secure an even distribution of the powder throughout the resulting composition. The composition is then permitted to cool to normal room temperature where it is found that the composition is a plastic.

Satisfactory thermal plastic sealing compositions result where from 5% to 22% by weight of copal and from 35% to 43% by weight of castor oil is employed as the binder for from to 35% by weight of the finely divided metallic powder. If more than 22% by weight of copal is employed, it is found that the resulting composition is too stiff for practical use.

A stiff paste or composition that has been found to be satisfactory comprises the following ingredients in the proportions given and mixed as hereinbefore described:

Per cent (by wt.)

Copal 15.93 Castor oil 37.17 Aluminum powder 46.9

In order to secure a softer paste or composition the quantity of castor oil used is increased and the resin content is decreased. In practice, a satisfactory soft paste or composition may be made from the following ingredients in the proportions given when mixed as hereinbefore described.

Per cent (by wt.)

Copal 10.3 Castor oil 41.2 Aluminum powder 48.5

These compositions when mixed as hereinbefore described, have the properties of remaining pliable and adhesive at as low a temperature as 35 C., and they are non-sagging at temperatures of up to C.

In practice, it is found that the compositions hereinbefore described when applied between the coils and the side of the food compartment in refrigerator evaporators are quite efiicient for conducting the heat from the food compartment to the refrigerator coils.

Although this invention has been described with reference to a particular embodiment thereof, it is, of course, to be understood that different modifications thereof are possible. This invention is, therefore, not to be restricted except insofar as is necessitated by the prior art and 1. A plastic sealing composition comprising, in

of copal, damar and kauri, and from about 35% to 43% by weight of a non-drying oil.

2. A plastic sealing composition comprising, in combination, from about 60% to 35% by weight of copper powder for providing thermal properties to the composition, from about 5% to 22% by weight of a natural resin selected from the group consisting of copal, damar and kauri, and from about 35% to 43% by weight of a non-drying oil.

3. A plastic sealing composition comprising, in combination, from about 60% to 35% by Weight of aluminum powder, from about 5% to 22% by weight of a natural resin selected from the group consisting of copal, damar and kauri, and

from about 35% to 43% by weight of a non-drying oil.

4. A plastic sealing composition comprising about 10% to 16% by weight of copal, about 41% to 37% by weight of castor oil, with about 49% to 46% by Weight of aluminum powder.

5. A plastic sealing composition comprising about 10.3% by weight of copal, about 41.2% by weight of castor oil with about 48.5% by weight w of aluminum powder.

6. A, plastic sealing composition comprising about 15.93% by weight copal, about 37.17% by weight of castor oil, with about 46.9% by weight of aluminum powder.

BYRON V. MCBRIDE. 

